Al Shaddad Bin Aous has quoted this tradition of the Holy Prophet (S.A.W.) "God calls for mercy in everything, so be merciful when you kill and when you slaughter, sharpen your blade to relieve its pain".
Many allegations have been made that Islamic slaughter is not humane to animals. However, Professor Schultz and his colleague Dr. Hazim of the Hanover University, Germany, proved through an experiment, using an electroencephalograph (EEG) and electrocardiogram (ECG) that *Islamic slaughter is the humane method of slaughter* and captive bolt stunning, practiced by the Western method, causes severe pain to the animal. The results surprised many.Experimental Details:
1. Several electrodes were surgically implanted at various points of the skull of all animals, touching the surface of the brain.
2. The animals were allowed to recover for several weeks.
3. Some animals were slaughtered by making a swift, deep incision with a sharp knife on the neck cutting the jugular veins and carotid Arteries of both sides; as also the trachea and esophagus Halaal Method.
4. Some animals were stunned using a captive bolt pistol humane slaughter by the western method.
5. During the experiment, EEG and ECG were recorded on all animals to record the condition of the brain and heart during the course of slaughter and stunning.Results and Discussion:

I - Halaal Method
1. The first three seconds from the time of Islamic slaughter as recorded on the EEG did not show any change from the graph before slaughter, thus indicating that the animal did not feel any pain during or immediately after the incision.
2. For the following 3 seconds, the EEG recorded a condition of deep sleep - unconsciousness. This is due to a large quantity of blood gushing out from the body.
3. After the above-mentioned 6 seconds, the EEG recorded zero level, showing no feeling of pain at all.
4. As the brain message (EEG) dropped to zero level, the heart was still pounding and the body convulsing vigorously (a reflex action of the spinal cord) driving maximum blood from the body: resulting in hygienic meat for the consumer.

II - Western method by C.B.P. Stunning
1. The animals were apparently unconscious soon after stunning.
2. EEG showed severe pain immediately after stunning.
3. The hearts of the animal stunned by C.B.P. stopped beating earlier as compared to those of the animals slaughtered according to the Halaal method resulting in the retention of more blood in the meat. This in turn is unhygienic for the consumer. (Many thanks to Muslim Students Organization - University of Miami)
Western Method used on cattle before slaughter can send brain tissue scattering throughout the animal, which could provide a route for madcow disease.

Slaughtering Beasts Before Death Guarantees Purification Of Flesh & Being Free From Microbes & BacteriumIn Quraan, Allah says:
Forbidden unto you (for food) are carrion and blood and swine flesh, and that which hath been dedicated unto any other than Allah, and the strangled, and the dead through beating, and the dead through falling from a height, and that which hath been killed by (the going of) horns, and the devoured of wild beasts, saving that which ye make lawful (by the death stroke), and that which hath been immolated unto idols. And (forbidden is it) that ye swear by the divining arrows. This is an abomination. This day are those who disbelieve in despair of (ever harming) your religion; so fear them not, fear Me! This day have I perfected your religion for you and completed My favor unto you, and have chosen for you as religion AL-ISLAM. [Al_Quraan.005:003]
This case of Islamic sacrifice by slaughtering - legitimate - beasts before eating is one of the cases used against Islam based on unawareness of The Divine orders, which are perfect and complete. Many debates with Islamic, minor, communities in Britain, USA, France, and other western countries regarding this case, specially societies caring for animals which condemns this rite and tries to show the sheep, after being slaughtered, while they are kicking and twisting in pain, and thus accusing Muslims by savagery and wildness. This position, in addition to being a face of spite and distortion, is considered a duplicated unawareness of what has been discovered and proven through the modern science.
In what follows we try to show the wisdom behind this Islamic way of slaughtering and why the other kinds, mentioned in the holy verse above, are forbidden, in the light of the modern science:The Carrion and Blood:
The carrion is a store of microbes and severe diseases. Consider if we put one gram of blood and one gram of flesh in an open place, and then, after 3 or 4 hours, we wanted to eat them ... will this cause any harm?
YES ... a severe harm. For the blood, the disease causing microbes are likely to be transferred to it through the knife used for slaughtering, or through the surrounding air, or maybe from any close source. When a microbe gets into blood it's geometrically multiplied every 30 minutes and becomes 2 microbes. Assume that 1000 microbes got into that gram of blood, then after 30 minutes they become 2000, and after an hour they become 4000, and after one hour and half they become 8000.... Thus after the 3 hours the number of microbes increase to become 64000 microbes in that gram of blood. It's well known that blood already contains a huge amount of microbes, even after death it becomes much harmful if drunk or stored then drunk.
And what about the piece of flesh?
Regarding the piece of flesh, microbes start by attacking the outer surface by destroying the hard layer which microbes can't penetrate, then a great amount of them dies because of shortage of nurture and incapability of reproduction. When the cook tends to cook this piece, he first washes it from outside, thus an amount of microbes is removed, and then by cooking an additional amount is killed.The Swine Flesh:
A so-called microbe, Yarsine, wasn't found except in the swine flesh, and it lives in a very low temperature around -40C. Many Europeans are infected by this microbe, and it's the responsible for many of backbone and joints diseases. Research proved the existence of this microbe in water and many sorts of food, but when human eats them it isn't as harm as those in the swine's mouth which is considered a suitable environment for it to grow.
Although swine is treated by penicillin and many antibiotics, it carries a lot of bacterium, and day after another science exposes a new disease caused by eating swine flesh. Some statistics showed a new infection by tapeworm in Denmark, and it's known that the life cycle of tapeworm takes place only in man or swine!!The Strangled:
Is there any harm caused by eating the flesh of a strangled beast?
A relation was recently discovered between the human health and the diseases by which the strangled beast was infected. The wall of the large intestine acts as a barrier preventing passage of microbes from inside the large intestine - where excrements exist - to the beast body and blood as long as it's alive. When the beast is strangled it slowly dies. This slow death is dangerous because the resistance of the wall of the large intestine is gradually lost causing the harmful microbes to pass to blood and flesh, and through blood circulation these microbes are further transferred to all parts of the beast, which haven't died yet. Moreover, microbes get through the blood vessels to flesh because of low resistance of those vessels membranes. The beast thus becomes a store of harmful microbes after death.The Dead through Beating:
Is there resemblance between death by strangling and beating?
Yes, the beast, which dies through beating also, suffers slow death exactly the same as the strangled, and the same scenario happens here. In addition: beating causes disruption of vessels and cells in the position of beating, so a mixture between blood components and cells components occurs, and probably causes interaction of toxic materials. That's why a tumor appears at the beating position. It's caused by these toxic chemical interactions, besides the slough skin. Thus the beast dead through beating has become a store of harmful microbes dangerous for human health.The Dead through Falling from a Height:
The beast may die differently by falling from a height … then what about its flesh?
The beast, which dies in that way, is just like which dies through beating, because in the position of falling the disruption occurs and it slowly dies. Even if it died just after falling, the microbes rapidly attack its body and that's why rottenness appears soon on its carrion, as a sign of the dangerous microbes inside it.The killed by horns:
Some beasts die by each other's horns, is there any danger caused by eating the flesh of them?
Dieing like that is similar to death through beating, but even more dangerous. Often, when a beast butts by its horns it hits abdomen position, specially in the intestine, so the dirty horn gets into the blood in the intestine of the other beast, and this polluted blood circulates in its body causing death. It's a true danger to eat such flesh.The Devoured of Wild Beasts:
When a wild beast ravens some beast, then what about eating its flesh?
It's well known that the claws of a wild beast are filled with microbes, and when it sticks them into the other's body the microbes moves through its blood, thus it slowly dies and becomes a store of harmful microbes.Saving that which Ye Make Lawful [The Wisdom of Islamic Sacrifice]:
What if a beast was exposed to any of the above methods, but it remained alive till we slaughtered it before it dies?
Thus we have extracted the main source of transferring microbes, that's blood, and they can't go further to other organs.
When a beast is slaughtered before death then its body gets rid of this substance, which spreads microbes inside it, because blood is the important biological liquid in the body of a living being, and which can resist millions of parasites through white corpuscles and antibodies as long as the living being is still alive in its natural temperature. But when it dies and blood stops circulation, microbes faces no resistance, and in this case the best way is to completely pour out that blood from the body as soon as possible.Mercy for Animals in Islam:
When we slaughter a beast and cut its vessels, does it feel pain?
The answer is simple: try to press any person in the same position of slaughtering; he will fall faint in moments. The centers of pain sensing become inoperative if the blood pumping stopped for 3 minutes only, because they need Oxygen continuously.
How can we say that the beast doesn't feel any pain while we find it kicking and twisting in pain?
This is because the nervous system is still working and it just lost its awareness. Since the neck wasn't broken yet, then the nervous system isn't invaded and so still working. In the Islamic way of sacrifice the nervous system tends to sending signals from brain to heart requesting blood because it has depletion of it, and signals to muscles to send blood to heart, and signals to whole body to help brain by sending blood.
Immediately, the muscles shrink and a strong movement happens in the guts and interior and exterior muscles, pressing strongly to pump all of the blood to heart, which in turn beats rapidly to be full of blood, and then sends it to the brain. However, on the way, blood gets out of the body through the cut vessels and don't reach brain. So, we see the beast twisting and bleeding until its body becomes empty of blood … thus it gets rid of the main environment of microbes growth.
Thus the slaughtered beast dies in 3 seconds only if it's slaughtered in the right way, and what we see as kicking, twisting, spasm and the like are just indications of the still alive nervous system, while the slaughtered beast doesn't feel any pain.Conclusion:
All of these medical secrets and healthy insights were mentioned in The Holy Quran. {Falsehood cannot come at it from before it or behind it. (It is) a revelation from the Wise, the Owner of praise} [Al_Quraan.041:042]. It guides us to every benefit and warns us from every evil.